Compare the DNA of two people and you see about three million base sequence differences and compare the DNA of a human and chimp and you see about thirty million. This is out of about three billion bases total. So, at the DNA level, people are about 99.9% identical to each other and about 99% identical to a chimp. This just counts single base differences, and not copy number variations and such, but in general it is clear that we are remarkably similar at the DNA level to chimps.

So why are we so incredibly different from chimps?

One view is that we really are not that different. Oh sure, we have Apple computers, Rocket Scientists and Astrophysics. But maybe if you could just tweak a chimp’s brain a tiny bit, and give him language, and books, and a few thousand years, then maybe chimps could have that stuff too.

But are big brains all that they are cracked up to be? A sperm whale brain weights 7800 grams, an elephant brain weighs 7500 grams and a person’s weighs 1500 grams. Are whales and elephants really that much smarter than us?

And are those people with bigger brains smarter than those with smaller ones? Big people tend to have big brains. Are football players and basketball players smarter than the rest of us? Men tend to be bigger in general, and to have bigger brains than women. But are they smarter?????

But maybe it is brain size as a proportion of body size. Our brains are about 2% of body weight. A dolphin brain is about 1%, and whale brains come in at around 0.1%. So this might start to make sense. But what about the mouse! It comes in at 3%!! http://www.highnorth.no/library/myths/br-si-bo.htm

Or maybe it is a special version of the Foxp2 gene that gave us improved brain wiring and speech. People with mutations in this gene have verbal dyspraxia, a severe speech and language disorder. Indeed, some have called this the “language gene”. Chimps have an altered version of this gene, and some suggest that this single difference accounts for a big part of the chimp-human disparity.

Or maybe it was a change in head musculature that allowed our craniums to expand more and accommodate larger brains. It has been shown that humans carry an abnormal version of a muscle myosin gene named Myh16. Stedman has suggested that his resulted in weaker and smaller jaw muscles, which in turn allowed the cranium to expand more and accommodate a bigger brain (http://www.ncbi.nlm.nih.gov/pubmed/15042088).

Or maybe it is related to genes that seem to directly control brain size. People with altered versions of these genes suffer microcephaly, or small heads and brains. One view is that people in general have macrocephaly, or big brains, compared to other species, because of special Homo sapiens versions of these genes. http://www.walshlab.org/

Or maybe we aren’t all that incredibly special at all???? Maybe, again, it is just language and culture that separates us from chimps.

Last Tuesday in Mississippi the “personhood amendment” garnered only about 42 percent of votes and (fortunately) did not pass. This proposed amendment to the State Constitution stated, “life of an individual begins at fertilization, cloning, or the functional equivalent thereof”. We wish to comment that this interpretation should raise serious doubts and concerns.

The proposed amendment was extreme, likely banning abortion even in cases of incest or rape, and even when the Mother’s life is threatened, and prohibiting in vitro fertilization, which results in embryos that are not used. As a result many prominent Doctors, Nurses and Clergy spoke out against it, contributing to its defeat.

The “Personhood Movement”, however, vows to continue its fight, and plans to propose similar constitutional amendments in other states, including Ohio. Since we might be casting critical votes in the relatively near future it is perhaps time to revisit the question of when during development we become a “person”.

One view, supported by the Personhood Movement, is that this occurs at the moment when two living cells, the egg and sperm, join to form the fertilized egg. From some perspectives this is an attractive answer. This is a well-defined event, and marks the point where a unique genetic combination is created. This is certainly when the embryo begins its developmental voyage to birth and beyond.

But there are some problems with this conclusion. First, most people are surprised to learn that about half of fertilized eggs do not normally survive to birth. The majority of these are lost very early in pregnancy, failing to implant into the wall of the uterus, well before the Mother even knows she is pregnant. If these very early embryos are full-fledged people then this is a catastrophe of major proportions. Think of it, for every person that is born there is a person that dies before birth. That is a lot of death.

It is also interesting to consider the remarkable ability of single early embryos to give rise to more than one person. We see identical twins, triplets and so on fairly routinely. Indeed, each cell of an eight cell embryo is able to independently make a complete person. If a single soul enters an embryo at conception, as some religions assert, then what happens to that soul when an embryo splits into multiple people? Do they each get but part of a soul?

For the sick and aged we have some fairly explicit criteria to determine when life is over and it is OK to “pull the plug”. In particular, if brain activity ceases then one is considered medically dead. For some it might seem appropriate to apply the same rules to the beginning of life. Very early embryos have no brains, as they are just one or a few cells. They are not conscious and can feel no pain.

So where does one draw the line? According to the Catholic and Evangelical view life begins at fertilization. At the other extreme, the Jewish view is that Human life begins with the first breath, as the head emerges from the womb. Most of us would likely place the time of “personhood” at some point in between.

There are no easy answers, but last Tuesday the people of Mississippi spoke, and declared that the proposed extreme amendment was unacceptable.

We got her about twelve years ago, as a little fluff of fur puppy that was happy as a lark, jumping around and into endless mischief. What a joy to be around. She grew up quickly to a medium-sized dog, but still full of energy, and happy to run around in big circles in our yard.

Whenever I came home she would be at the door to greet me, tail wagging, and acting like it was the best moment of her day. Each time she would bring me her favorite toy, a little stuffed animal. I never fully understood the significance, but I always thought it was a generous and loving gesture.

Some things would scare her to death. She hated thunder and whenever a big storm would pass through in the summer she’d be petrified, just shaking with fear. And I thought it was strange that she hated for me to sneeze, which would also make her tremble uncontrollably and look for a place to hide.

She had peculiar tastes. We had to protect the cat box from her. Once she got into our dirty clothes and ate about ten pairs of my dirty underwear, focusing on the apparently tastier crotch regions. This clogged up her intestines and required some serious surgery to fix.

She had a pretty good vocabulary. She certainly understood the word NO! And if we told her to go to her room she would head off to the laundry room. She also knew the words “upstairs”, “downstairs”, “inside”, “outside” and she could do a few tricks.

She spent a lot of time playing with our cat, which was her best buddy. Their favorite game was to take turns chasing each other around the house at full speed. But when they were worn out they’d lie down next to each other and rest.

Once we left her at someone’s house for a week while we went on vacation. When I went to pick her up I was worried she might have forgotten me. But no, it was the most incredible reunion you could imagine. Her tail was wagging so fast that it shook her whole body. She was absolutely frantic with excitement. She wanted to run, but she wanted to be next to me. She was the happiest thing on the planet. She peed all over the floor.

My dog was my friend, always there when I needed her. I know she loved me, despite my many flaws.

Benjamin Franklin wrote in 1789, “The only things certain in life are death and taxes.” Well, for the last couple of years General Electric has shown that it is possible to make billions and pay no taxes. And some recent startling advances in aging research suggest that Ben might have been wrong on both counts.

A unifying theory of aging is beginning to emerge. It explains many previous and apparently disjointed observations through a common mechanism. Let’s call it the Continued Accumulation of Crud with Aging, or CACA model.

It is no surprise that unwanted junk accumulates in cells with age. Some organelles, such as mitochondria, can break down, and sit around useless. Protein aggregates, or clumps, can form with time.

Cells have developed a sophisticated mechanism to eliminate unwanted material. It is referred to as autophagy, or self eating. The process is pretty amazing, and still not completely understood. First cells need to be able to recognize the things to eliminate. Then they engulf them with a membranous structure called an autophagosome, which then fuses with a stomach like structure called a lysosome, which breaks things down to small subunits that can be re-used by the cell.

It turns out that many things that activate autophagy can prolong lives.

Caloric restriction, or simply eating less without malnutrition, has been shown to significantly extend lifespan in a wide variety of model organisms, including mice, rats, fruit flies and dogs (http://en.wikipedia.org/wiki/Calorie_restriction). And as might be expected, caloric restriction promotes autophagy. When cells aren’t given enough to eat they begin to self-cannibalize, or eat themselves.

It is also interesting to note that an unbiased screen for genes involved in aging in yeast found many genes that function in autophagy. It turned out that inactivation of these same genes in fruit flies also reduced life span, resulting in the accumulation of dysfunctional mitochondria, muscle degeneration and heart malfunction.

It has also been shown that the drug rapamycin can dramatically extend the life span of yeast, invertebrates, and mice (http://www.nytimes.com/2009/07/09/health/research/09aging.html). Although rapamycin has many effects, and the best advice at present is please don’t try this at home, one of the key functions of this drug is to activate autophagy.

It is also interesting to consider the correlation between body size and longevity (see The Comparative Biology of Aging, by Norman S. Wolf). In general smaller animals have shorter lives than larger ones, with mice for example living only a couple of years, while people, horses and elephants can live for decades. But within a species there is often an inverse relationship, with smaller dogs for example living on average much longer than big dogs. The bigger dogs are known to have elevated growth hormone and insulin like growth factor signaling, which inhibit autophagy.

An important recent advance came from the study of people with Progeria, who show extremely rapid aging. Although apparently normal at birth they typically present symptoms before the age of two. They grow slowly, lose their hair, have fragile bones and thickened skin, and usually die in their teens from heart attack or stroke. The disease is caused by a mutation that results in the accumulation of an abnormal protein called progerin, which results in time in their cells showing nuclear blebbing, a very abnormal and sick structure.

Francis Collins, the Director of the National Institutes of Health, and his colleagues recently published an important study of the effects of rapamycin on Progeria patient cells grown in culture. They showed that rapamycin can cure the cells of nuclear blebbing by promoting the clearance of progerin through autophagy (Science Translational Medicine, June 29, 2011). To quote their paper, “the results reported herein support rapamycin as a potential treatment for children with Progeria.”

And, if we can learn how to effectively treat the accelerated aging of Progeria it raises the possibility that in time we might be able to treat the normal aging process that we are all currently experiencing. Of course the CACA model does not explain all of aging. There are additional forces at work. But ever increasing evidence argues that it is a very important component of the aging process.

But should we cure aging, even if we could?? Some would argue that aging and death are good things. After all, don’t we have too may people already? But who on earth would refuse an offer of an additional ten, or twenty, or even fifty years of healthy life?

Eggs and sperm are pretty special cells. They are the chains that link one generation to the next. In a sense they are our immortal parts, with some living on in our children, and some of theirs carrying on in yet the following generation, and so on. The scientists that study these cells consider them the most important cells of the body. Without them our species would cease to exist.

Infertility is a devastating condition for couples that desire children. They will go to great lengths to overcome the problem. About one percent of all births in the US are the result of in vitro fertilization procedures. But even these so called test tube babies can only be made if the parents produce eggs and sperm. If the male, for example, makes no sperm, then all current procedures fail.

A remarkable breakthrough in the test tube creation of sperm has been reported in the Aug. 19 issue of the prestigious science journal “Cell”. A group working at Kyoto University, including Katsuhiko Hayashi and Mitinori Saitou, discovered how to turn stem cells into sperm. They worked with the mouse model organism, but there is no reason to think that the same developed methods won’t also apply to humans.

This group and others had been previously studying the normal progressive process that creates sperm. It had been shown that in the embryo the stem cells that will normally give rise to sperm are sequentially exposed to a series of signals including the Wnt, Activin and FGF, BMP4 and LIF growth factors. By recapitulating this natural plan in the petri dish they found they were able to convert a small percentage of stem cells into primordial germ cells, the precursors to sperm. They were able to actually sort out just the primordial germ cells based on their surface properties, and then they injected them into the testicles of mice that could not make their own sperm. Amazingly, the injected cells made sperm and the mice became fertile.

This work was first carried out using embryonic stem cells, which are natural stem cells that were isolated from mouse embryos. This is great from a science perspective, but it wouldn’t be of much use for an adult male, with his embryonic stem cells long gone. The Kyoto group therefore repeated the experiments starting with stem cells that had been made from adult cells. Yamanaka had shown previously that it is possible to treat adult cells, such as skin cells, with a special gene expression cocktail and to turn them into the functional equivalent of embryonic stem cells. See my blog on “Why Yamanaka will win the Nobel Prize” for details. Anyway, they showed that the procedure worked just as well with stem cells made from adults.

The implications of the work are enormous. In a few years, as these procedures are translated from the mouse to the human, it might become possible for men that don’t make sperm to father children. This could provide considerable benefit for otherwise infertile couples.

It also opens up some interesting possibilities concerning designer genes children. Scientists are already incredibly proficient at the genetic engineering of stem cells. Over ten thousand genes have been modified in mouse stem cells, and then the cells were used to make mice, which then revealed the functions of the genes. It now appears possible to take skin cells from adults, to turn them into stem cells, which can then be genetically manipulated, and turned into sperm. That is, it now appears possible to make designer genes sperm.

As we better learn the complex relationships between DNA sequence and traits, such as longevity, health, looks, athletic performance and intelligence, it will become possible to engineer sperm that will produce children with desired features. This strategy is much more ethically appealing than more traditional designer genes baby approaches, which typically involve the genetic screening of many embryos to find those with the preferred gene combinations. The problem, of course, is that those embryos without the wanted features are discarded.

But the designer genes production of sperm, and eventually eggs, avoids these ethical concerns. All of the genetic engineering and selection occurs before any embryos are made. No life is lost. No embryos are harmed. What is not to like?

Historians might refer to our current era as the Age of DNA Sequencing. There is an incredible technological revolution going on that is radically reducing the cost of DNA sequencing. The Human Genome Project, which determined the first complete Human DNA sequence, was completed about a decade ago, at a cost of over three billion dollars. It was a remarkable achievement, to be ranked with the likes of landing on the moon, and with much greater long term impact on our well being.

Yes, there was a bit too much hype, and some are disappointed that we haven’t seen more diseases cured. But there is no denying that we have set out on an incredible journey that will, in time, completely change the nature of medicine. Indeed, it is even going to change the fabric of the Human species itself.

The first thing we discovered is that people only have about 25,000 genes, a number about five fold smaller than previously thought. It is amazing to think that you can genetically program all of the complexities of a person starting with only 25,000 genes. The Human DNA sequence also allowed us to map thousands of mutations to specific genetic diseases. For many diseases this work provided the first clue as to the genetic basis, and put us on the path to finding a cure.

One important offshoot of the DNA sequencing work is the field of personalized medicine. Our genetic differences make us respond differently to medicines. A drug that might cure one patient could kill another. Already we find certain cancer treatments are guided by the genetic basis of the individual’s disease.

Another result is the appearance of several companies that offer individual genetic analysis services. These companies, like 23and me, Pathway Genomics and Navigenics, all use a relatively simple “SNP Chip” technology that looks at thousands of bases, of the 3 billion total, that have been associated with specific interesting traits. The cost is generally a few hundred dollars, and the companies promise to provide “insight into your traits, from baldness to muscle performance. Discover risk factors for 97 diseases. Know your predicted response to drugs, from blood thinners to coffee. And uncover your ancestral origins.” https://www.23andme.com/.

But the real revolution is yet to come. The truth is that our current understanding of the genetic basis of most traits is fragmentary at best. We don’t really know which gene combinations define our features, such as appearance, intelligence, longevity, athletic performance and predisposition to disease. What we really need is the DNA sequences for lots of people, so we can then begin to relate their traits to their DNAs.

And this is why the current revolution in DNA sequencing technology is so important. While the first Human DNA sequence took many years to complete, at a cost of over three billion dollars, it is now possible to sequence a person’s DNA in a matter of weeks for a cost of a few thousand dollars. That is, the price has dropped about a million fold. And there is no end in sight. I was recently speaking with a representative of a company that makes the Ion Torrent DNA sequencing machine. It uses a modified computer chip to sequence DNA. He told me that the goal of his company is to increase the capacity of the machine by a factor of ten every six months. This absolutely blows Moore’s law out of the water. Gordon Moore, one of the founders of Intel, stated in 1965 that the capacity of computer chips could be expected to double about every two years. Interestingly, the first person to have their DNA sequenced with the Ion Torrent machine was Gordon Moore.

In the near future, as the price continues to plummet, we will each of us have our DNAs completely sequenced. Our DNA sequence will be an important part of our medical record, helping guide lifestyle choices, and telling the doctor which diseases to be on the lookout for.

We will then have DNA sequences for millions of people, instead of the thousands that we have today. The DNA sequencing revolution is going to allow us to crack the code, and to figure out which sequences are responsible for which traits. As we relate the sequences of all of these people to their traits we will be able to connect the dots, and learn the genetic equations that define health, longevity and intelligence.

And, as we combine the DNA sequencing revolution with concurrent revolutions ongoing in the fields of genetic engineering and stem cells, the Human race will for the first time be able to take conscious control of its own genetic destiny.

It could well mean the end of the Human race as we know it, but perhaps the beginning of something better.

In many ways our DNA defines us. Consider identical twins, which are the result of an embryo splitting in early life. They are actually a single individual that divided into two parts during the early stages of embryonic development. They don’t call them identical for nothing. Studies show that in addition to looking the same they are also extremely similar in almost all other measurable respects, including intelligence. And, of course, the reason that they are so alike is that they have identical DNA.

But what makes most people so different from each other? We are only beginning to understand how our DNA differences distinguish us. The Human Genome Project, finished about a decade ago, was a huge first step. It defined the sequence of the A, T, G and C building blocks of our three billion bases of DNA. Like the Moon Project, it was an amazing accomplishment for mankind.

In a sense it was like our DNA defined itself, through us. Our DNA, which encodes us, was actually able to determine its own sequence, using people as a tool for the process. A very smart molecule indeed.

One of the most incredible discoveries to come from the Human Genome Project was the remarkably small number of genes we have. It turns out that we only have about 25,000 genes!! This seems a pitifully puny number.

Think of it. We all start a single cell, a fertilized egg, a very small speck of protoplasm barely visible to the naked eye. And this one cell somehow turns itself into a complete person. And people are incredibly complicated. They can weigh one or two hundred pounds or more. They have arms and legs and complex organs like the liver, heart and kidney. And they have a brain, which has about 100 billion neurons with over 100 trillion specific interneuronal connections. Wow!! All of this from just a single cell equipped with a genetic program of only 25,000 genes in its nucleus. Truly amazing.

And then we sequenced the DNAs of several people, and compared them. It turns out that our sequences are about 99.9% identical, from one person to the next. Our individual differences are defined by the 0.1% sequence variation, the several million bases that fluctuate among the three billion total. As we sequence the DNAs of more and more people we will begin to define the complex equations that relate these sequence differences to specific traits.

And when we sequenced the DNAs of other animals we made more interesting discoveries. It turns out that all mammals-including lions, cows, pigs and elephants- also have three billion total bases of DNA, and about 25,000 genes. Indeed, we all have pretty much the same set of genes. To paraphrase Mario Capecchi, a Nobel laureate, who I once published a paper in Nature with, mouse and man are 99% genetically identical. What he meant by this is that for every gene a person has there is about a 99% chance that the mouse will have a corresponding very similar gene. All mammals have the same genes, but those genes will differ in exact base sequence from each other. His point was that the mouse is an excellent genetic model system for scientific study, because it so closely recapitulates man.

But another key conclusion is obvious. All mammals are very closely related.

But instead of looking at close relatives, let’s look at very distant relatives, like the fruit fly. Shockingly there is some fascinating evidence that we are even genetically related to these little bugs.

Geneticists discovered some crazy mutant fruit flies about a century ago. One mutation, for example, gave a fly that had legs growing out of the head where the antennae were supposed to be. Imagine that! During development the cells that were supposed to make antennae instead made legs that now protruded from the head! Another interesting mutation gave a fly with no eyes.

As technology advanced it became possible for us to manipulate the genes of the fly. We could alter the gene involved in leg/antennae development and re-create a fly with legs coming out of the head. But even more remarkable, we learned how to introduce human genes into the fly. And when we made similar alterations to the human counterpart of the fly gene, and put it in the fly, we got the same result, a fly with legs on the head! The human gene seemed to be functionally equivalent when placed in the context of the fly. A truly surprising and amazing discovery!

We could also take the fly gene found to be critically important for making eyes and cause it to be mis-expressed during development. It was found that if this gene was activated on the legs, for example, one could make a fly with extra eyes on its legs! Indeed it was possible to make a fly with lots of eyes, on the legs, on the antennae, and at other places on the body. But, once again, the most remarkable result came when we took the human gene most closely related to the fly eye gene and placed it in the fly. Just like for the fly eye gene, we found that if we turned on the human gene at various locations during development we could make a fly that had fly eyes all over its body. Once again, the fly and human eye genes appeared to be functionally equivalent.

These results show a remarkable, and quite unexpected, conservation of developmental genetic programs stretching across enormous evolutionary distances. Many human genes seem to work quite well, thank you, when functionally tested in fruit flies, where they initiate genetic cascades that drive the formation of discrete fly body parts. That is, in many cases fly and human genes are functionally interchangeable.

These experiments demonstrate evolutionary relatedness not only between chimps and people, but also between insects and people.

I recently blogged on a visit to the creation science museum, located not far from my home in Cincinnati, Ohio. It is a creationist alternative to natural history museums. The creation museum attempts to provide scientific authenticity and respectability to the creationist view that the bible is literally true in every detail. That is, God created all life on earth a few thousand years ago. And, at least at first, we lived in happy vegetarian harmony alongside lions, tigers, and of course the Tyrannosaurus rex. Indeed, one of the first exhibits shows people mingling with the dinosaurs.

The previous blog stirred a hornet’s nest of comments and I thought it would be useful to summarize some of the most interesting points, and to raise a few new ones. For the moment let us focus on Noah’s ark and the flood. One of the largest exhibits in the Creation Museum is dedicated to the flood, and the owners are now building a life size replica of the ark. Creationists clearly do not back away from a literal interpretation of the biblical flood.

First, where did all the water come from? The water levels of the oceans had to rise many thousands of feet to cover all of the mountains. And rain just recycles water. Water that evaporated from one place is dropped at another place. Rain can cause local floods, but not global ones. Creationists counter that water also squirted from the ground (“fountains of the deep”). Let me say, that is a lot of squirting.

Second, how did all of those animals make it to the ark? Polar bears, kangaroos, Galapagos finches, rocky mountain lions, and so on. The Creation Museum explains that a few thousand years ago there might have been only one continent, which then split into the several that we see today. Well, we do know that continents drift, but their movements are measured in inches per year, not the miles per year that this explanation would require.

And why didn’t any of the dinosaurs make it to the ark? I thought the bible said that two of every kind were included on the ark. And if dinosaurs cohabited the planet with people in pre-flood times why don’t we read in early bible passages of the occasional T. rex ravaging of villages?

Then there is this funny business of creationists believing in microevolution, but not macroevolution. The creation museum clearly states that one species can indeed evolve into multiple closely related species. This is required for the ark hypothesis to have a chance. The ark just didn’t have room for every single species of the planet to fit. So it is argued that the limited number of species that were saved by the ark then split into the incredible number of species that we see on the planet today. Unfortunately, for creationists, evolution is not that fast. A few thousand years is not even close to enough time to account for such diversification. Only in rare cases, where the driving force is human selection instead of natural selection, can speciation occur so rapidly. See my blog “Dogs prove evolution”.

And finally, and most importantly, there is the incredible moral dilemma of the flood. God knowingly, and with clear intent, killed every person on the planet, save a few. This must have included thousands of women with unborn babies in their bellies. God killed them. And think of the innocent children. It wasn’t their fault that things were going badly. They were just kids, having fun, playing their games, spending time with their friends, loving their parents. But God killed them. And think of all of the mothers of the planet, caring for their children, hoping for a brighter future, wanting the best for their kids. God killed them too.

God gave Moses the Ten Commandments to provide a moral compass. These were the essential rules to live by. To live a good life one should obey these commandments.

Thou shall not kill.

If the flood story is true then it would seem to represent a rather embarrassing inconsistency.

There is a quiet revolution going on in the world of cloning. Very few have heard of it, but its potential power is astonishing. Imagine a radical new way to clone that can not only create exact carbon copies of adults, but also allows the generation of important genetic improvements. Another you, but smarter, healthier, and maybe a bit better looking.

The birth of Dolly the sheep fifteen years ago shocked the world. We learned it is possible to replace the genes of an egg with those from an adult, and in a few cases the egg would proceed to make a viable clone, like Dolly. And the debates began! Should we allow human cloning? Was this a useful new reproductive option for childless couples? Or was it a crime against nature? Would clones have a soul? Were we moving towards a Brave New World future, with armies of clones fighting our wars and working in our factories?

The gene replacement technology used to make Dolly, however, was severely flawed. Only about one in a hundred eggs with genes from an adult survives. This procedure clearly should not be applied to people. For every birth there would be 99 aborted monstrosities, and even the rare clones surviving to birth are not really normal when examined carefully.

But recently we’ve seen a perfect storm of incredible advances in biology that changes everything. It is now possible to take adult cells, from the skin for example, and to transform them into stem cells, which can then be converted into complete individuals. It works quite well for mice, and there is every reason to think it would also work for humans.

How is this cloning through stem cells accomplished? The breakthrough was Shinya Yamanaka’s discovery that it is possible to treat adult cells with a special gene expression cocktail that turns them into the functional equivalent of embryonic stem cells. Stem cells, as the name suggests, are able to branch in many different developmental directions, to give rise to heart, nerve, liver, or other cell types. In the world of medicine, this is like the ancient alchemist somehow succeeding in turning lead into gold. Stem cells offer great promise in the regeneration and repair of diseased or damaged organs. Historically, the most powerful stem cells – those able to give rise to all of the different cell types of the body – were made from embryos. Hence the ethical controversy, since it was necessary to kill human embryos to make embryonic stem cells.

Adult derived stem cells made by the Yamanaka procedure, however, are as powerful as those made from embryos. They too can give rise to all of the cell types of the body. Indeed, it is possible to take adult derived mouse stem cells, grown in a plastic dish in the laboratory, and to turn them into complete mice. The controversy over human embryonic stem cells should now be officially over because we can make equally potent stem cells from adults, without sacrificing embryos.

Stem cell cloning, however, opens a Pandora’s box of possibilities. It is much more efficient than the gene replacement approach used to make Dolly. In addition, stem cells are extremely genetically malleable. Nobel prize winning genetic engineering technology works very well with them. It is therefore now feasible to clone not only exact copies, but also improved versions of people.

With the technical objections rapidly fading, it is now time to revisit the ethical issues of cloning. First, is it morally wrong to have multiple people with the same, or nearly the same, genes? Of course identical twins, triplets, quadruplets, and so on have long existed as a product of nature. But there are some differences between clones and twins. Twins are the same age, while a clone would be younger than its single parent. In addition, there is a limit on the number of genetically identical individuals that can be made by natural reproduction, but in theory a hundred or more clones could be made from one person. It makes most of us uncomfortable to think that a wealthy person could now make many young copies of him or herself.

Another issue is procreation without sex. Some people find the laboratory creation of human offspring repugnant, thinking it degrades and cheapens the process of reproduction. Are we heading towards a shopping catalog selection of our children? Nevertheless, the current methods of in vitro fertilization involve mixing eggs and sperm in the test tube, thereby creating human embryos for otherwise infertile couples. About one percent of all births in the U.S. are now the result of in vitro fertilization. Cloning technology is similar in principle, but using only one parent to make embryos instead of two. Does that difference make it morally wrong?

Our science and technology are marching forward at an ever accelerating pace. The topic could not be more important. We are talking about the nature of our children, and in the long run, our species. Genetic enhancement could lead to improved intelligence, and exceptionally long and healthy lives. Or a hellish dystopia. We must move into the future with great care.